<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div id="app">
    <button @click="increase">increase</button>
    <button @click="stop">stop</button>
    <br>
    {{count}}
  </div>
  <script type="module">
    import { createApp, ref, watchEffect } from './node_modules/vue/dist/vue.esm-browser.js'

    createApp({
      setup() {
        const count = ref(0)
        const stop = watchEffect(() => {
          console.log(count.value)
        })
        return {
          count,
          stop,
          increase: () => {
            count.value++
          }
        }
      }
    }).mount('#app')
  </script>
</body>
</html>